Why Sodium and Potassium are stored in kerosene?

Sodium and potassium occur-

Why is sodium stored in kerosine ?

Sodium- potassium pump is

Why are sodium and potassium not used to prepare hydrogen gas in the laboratory ?

Both sodium and potassium are present in equal abundance in the earth's crust, but sodium is about 30 times as abundent as potassium in oceans. Give reasons.